The great teaser, with the Doctor’s bemused words to camera, leads into the first half of the two-part Doctor who series finale.

Spoofing Big Brother (and Weakest Link for that matter) are a little pass&eacute even when it involves contestants dying (The Year of the Sex Olympics, which deals with a similar issue was broadcast in 1968), but it’s hard not to enjoy the bizarre crossover with Doctor Who. The incessant Big Brother music (if you’ve got the rights, flaunt them…) is a bit over the top but the housemates are fun pastiches, especially the camp Strood who offers crocodile tears – “it should have been me” – when Crosby is evicted. This is, however, followed by Lynda-with-a-y and one of the worst lines of the episode: “She’s been evicted…from life.”

One of Russell Davies’s best episodes, the cliffhanger is great. Who is the Bad Wolf? How did the Daleks survive? Will the Doctor win? And the Doctor’s final line is straight out of Big Brother: “I’m coming to get you!”

Boom Town, the eleventh episode of Doctor Who, was a late addition, apparently: an empty slot allowing it to be influenced by the previous episodes. We’re therefore rewarded with the return of one of the weaker villains of the series. I’m going to be nit-picky. Sorry.

If we take the episode at face value, it has been six months since World War Three. In that time Margaret Slitheen has become Lord Mayor of Cardiff, commissioned a nuclear power station and achieved the necessary go-aheads to build it. Given that the original Margaret Blaine was from MI5, she won’t have been involved in politics before her previous appearance. Are we to assume half the politicians in Cardiff have been bumped off? And a Lord Mayor doesn’t run the council, they chair council meetings and cut ribbons. If Margaret is a directly-elected mayor, her achievement is all the greater. Especially as she seems to have help on despite knocking down in her car one of the people involved in the nuclear project. Credit to Annette Badland, though: she’s much better than in her previous appearance with some notable moments, although stilly hammy at times. She also gets some good scenes: the line about London not caring about Wales and her various attempts to kill the Doctor in the restaurant (plus the mention of venom grubs) are highlights.

Jack is pretty redundant in the episode which is unfortunate as he’s only just been introduced. Meanwhile, characters make great leaps: the Doctor knows immediately that the power station is flawed; Margaret suddenly has great insight into the Doctor’s personality. The brief realisation about Bad Wolf is handled well: spooky and then funny. There are fewer special effects in this episode but the cracks forming in the ground around the TARDIS are great.

Russell T. Davies shows his strengths with his dialogue and the scenes between Rose and Mickey are perfectly pitched. It’s a shame, though, that we never got to see Rose’s first visit to an alien planet. Davies’s characters are let down a little by his plots. In this case the deus ex machina ending, to which he confesses in Doctor Who Confidential, is a disappointment.

But Boom Town casts itself as a morality tale and here it doesn’t succeed. It poses interesting questions about the Doctor’s willingness to kill – although he didn’t seemed bothered about finishing off the last of the human race a few weeks ago – but the opening rift and the Slitheen’s return to traditional monster mode let him off any decision. When Margaret asks the TARDIS crew and Mickey to look her in the eye, no-one dissents so there’s no drama between them.

Some good lines but it feels like filler before the finale.

You wait 16 years for a great episode of Doctor Who and then three come along at once.

From the wonderful resolution of the cliffhanger to the glorious denouement of the story, The Doctor Dances positively sparkles. The script is packed full of terrific ideas (“Squareness gun. Like it”), good jokes and lovely dialogue. The interplay between the Doctor, Rose and Jack is great fun (“Who looks at a screwdriver and thinks ‘This could be a little more sonic’?”) – the sort of scenes familiar to viewers of the writer’s award-winning previous work, from Press Gang to Coupling. Steven Moffat is the only writer on the series who’s been scripting TV for as long as Russell T. Davies and it shows.

My only niggle plotwise is that the nanogenes don’t seem to try to turn the Doctor human (given that his DNA is presumably quite different from human DNA) but I’m sure The Fans can come up with a reason. Quite frankly, when an episode is as good as this, who cares?

There are shocks and surprises throughout. Jamie appearing in his room; Mr Lloyd’s dalliance with the butcher; the possessed typewriter; and the answer to “Are you my mummy?” Murray Gold’s score is his best of the series so far: evocative, suspenseful and never intrusive.

All these elements build up to a thrilling, positive finale. The idea is terrific, that after such a dark story everyone not only survives but is physically better than before. (Which counterpoints one of the best “classic Who” stories, The Caves of Androzani, in which nearly everyone – including the Doctor – dies.) For the first time in a while, the Doctor explicitly saves the day. Jack gets to straddle a bomb, Dr Strangelove style (is that “Bad Wolf” in German on the side?) and everyone lives happily ever after.

In summary: this two-parter is possibly the best Doctor Who story ever made. As one friend texted me, “Steven Moffat's got the moves.” Could there be better news than that he’s writing for series two?

How great is this? Just when you thought New Who couldn’t get any better, we’re treated to another great episode. There’s no doubt at all that this really is Doctor Who – and it’s great.

The dramatic opening of The Empty Child quickly gives way to a build-up of spookiness. The ringing TARDIS phone is eerie as is the titular child. (Although when he called to the Doctor through the letter box, he could’ve been asking “OK. Is Dave there?”)

The sonic screwdriver now seems to be acting as a tricorder (which Russell Davies justifies in the Doctor Who Confidential following the story’s conclusion) and the Doctor’s “damp island” speech is touch on the Land of Hope and Glory side – although only a touch. Oh, and the Union flag on Rose’s t-shirt is wrong, but that may well be intentional and just makes it an authentic t-shirt…

For the first time this series, the episode feels perfectly structured: neither two fast or two slow at moments, but just right. The child actors are uniformly good and Richard Wilson proves that guest stars in Doctor Who can be excellent.

The dialogue is great throughout. The exchange between Rose and Jack about her “cellphone” is amusing and well-observed. The scene in the bar is a nice touch but there are moments of darkness, especially the suggestion that the evacuated children were victims of abuse.

An excellent cliffhanger leaves you wanting more and the second-half will determine whether the story as a whole is a great as the promise of The Empty Child.